HOUSTON (AP) - A glimmer of hope surfaced this week in the effort to keep the Houston Astrodome from being torn down with the addition of the building, the world's first multipurpose domed stadium, to the National Register of Historic Places.

But the designation alone will not be enough to prevent the demolition of the so-called "Eighth Wonder of the World," according to officials.

The Astrodome's fate has remained uncertain since voters in November rejected a proposed $217 million bond issue to redevelop the stadium into a giant convention and event center. It had been home to baseball's Houston Astros and the NFL's former Houston Oilers.

The National Park Service announced this week the Astrodome had been added to its National Register of Historic Places, joining more than 1.5 million other buildings and properties.

The designation, mostly honorary, means any effort to revamp the stadium can be eligible for federal and state tax credits as well as other economic incentives, said Paul Lusignan, a historian with the National Register of Historic Places in Washington, D.C.

But the designation doesn't place any rules on what Harris County, which owns the stadium, can do with the facility.

"A listing in the register doesn't freeze the property and make it untouchable," Lusignan said

Joe Stinebaker, a spokesman for Harris County Judge Ed Emmett, said the designation will have "very little impact" on the county's decision making process.

Stinebaker said the Astrodome's fate is currently "in utter limbo" as county commissioners have no timeline for deciding what to do with the structure.

No serious private or public proposals for revamping the Astrodome have been presented to county leaders since the bond issue was struck down by voters, he said.

"We get many ideas on what should be done. But none of those proposals ever include financing, which is really key to the whole thing right now," Stinebaker said. "Any savior at this point would have to come from the private sector."

Beth Wiedower, senior field officer with the National Trust for Historic Preservation, one of various groups working to save the Astrodome, said she hopes this week's designation will aid efforts to find either a private entity or a public-private partnership that will invest in reusing the stadium.

"I'm more optimistic today than I have been since the election," she said.

Opened in 1965, the Astrodome hasn't been home to a sports team since 1999 and has been closed to all events since 2009. While still structurally sound, the iconic stadium had fallen into disrepair. Stadium seats, pieces of AstroTurf and other Astrodome items have been sold to the public in recent months.

The stadium's most prominent use in recent years was as a shelter for Louisiana residents displaced by Hurricane Katrina in 2005.